Doc: Dengue-free areas not always safe
If no preventive measures taken, they may become fertile ground for outbreaks, says Dr Sazaly
Communities free of dengue may become complacent, but they should not. Prof Dr Sazaly Abu Bakar
PETALING JAYA: The fight against dengue should emphasise preventive measures in areas thought to be free of the disease, a virologist said.
Prof Dr Sazaly Abu Bakar of Universiti Malaya said this was because data showed dengue outbreaks tend to happen in such areas.
This was evident in new housing estates and high-mobility areas with residents moving out and new ones coming in, said Dr Sazaly, who presented a paper on the role of popula- tion immunity in shaping recurring dengue during the National Dengue and Arboviruses Infection Conference 2017 on Saturday.
During an outbreak, after the population in an area has been exposed to the virus, it develops a general immunity because fewer susceptible people are left to be infected. This makes it harder for the virus to spread.
“As long as our immunity is good, we are protected. But if we have enough people coming in who have not had dengue, the population immunity will dip. That is why we keep having dengue outbreaks,” he said in an interview.
Section 7 in Shah Alam, for example, used to be dengue-free but when a new residential area was developed, people from outside the area – who have not been exposed to the dengue virus – came there to live and subsequently, he said, a dengue outbreak occurred there.
“Hotspots (are) cyclical because after a few years, a new group of people who never had dengue before would move into the area and when there are enough of them, that’s when an outbreak will occur again,” he said.
Dr Sazaly pointed out that dengue incidents in Petaling Jaya and Kuala Lumpur were dropping because the population had been “immunised” in previous outbreaks.
Instead, the outbreaks are now occurring on the periphery of the cities and in new urban centres, he added.
For this reason, Dr Sazaly urged communities to carry out preventive measures such as eliminating mosquito breeding grounds even if their areas were relatively dengue-free.
“Residents’ associations should play a role in looking after their own communities. Communities free of dengue may become complacent, but they should not,” he said.